Added sponge notes to the knowledge base

knowledge base/sponge.md

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+# Sponge
+
+## TL;DR
+
+```shell
+# installation
+brew install sponge   # or moreutils
+
+# append file content to the source file
+cat path/to/file | sponge -a path/to/other/file
+
+# remove all lines starting with # in a file:
+grep -v '^{{#}}' path/to/file | sponge path/to/other/file
+```
+
+## Further readings
+
+- [mankier man page]
+- [tldr live demo page]
+
+[mankier man page]: https://www.mankier.com/1/sponge
+[tldr live demo page]: https://tldr.ostera.io/sponge